[NEW] Option -f is added.

[NEW] Option -f is added.

[IMPROVED] Diagnosis of looped dependencies is implemented at the phase of "Completion of *-time requirement lists" in the preparation stage.

The manual page was modified in the part of options and history.
The target version is increased.
The copyright years are updated.

Changes to be committed:
	modified:   README
	modified:   bin/portsreinstall
	modified:   lib/libcommand.sh
	modified:   lib/libconf.sh
	modified:   lib/libdatabase_build.sh
	modified:   lib/libdatabase_query.sh
	modified:   lib/libdatabase_record.sh
	modified:   lib/libdeinstall.sh
	modified:   lib/libfileedit.sh
	modified:   lib/libmessage.sh
	modified:   lib/libmisc.sh
	modified:   lib/liboptions.sh
	modified:   lib/libpkgsys.sh
	modified:   lib/libprogram.sh
	modified:   lib/libreinstall.sh
	modified:   lib/libstr.sh
	modified:   lib/libtemp.sh
	modified:   lib/libusage.sh
	modified:   man/portsreinstall.8